Heat exchange unit



Feb. 6, 1951 R. w. KRlTzER 2,540,339

HEAT EXCHANGE UNIT Filed Juno 14, 1948 ll Il mmm.

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Patented Feb. 6, 1951 UNITED STATES PATENT OFFICE HEAT EXCHANGE UNIT Richard W. Kritzer, Chicago, Ill. Application une 14, 1948, Serial No. 32,876

3 Claims. 1

The invention relates to cross-iin heat exchange units.

One object of the invention is to provide a heat exchange unit which includes serpentine tubing, cross-fins provided with slots for the side entry of the tubing and interlocked with expanded tubing, the cross-fins being provided with integral teeth for spacing the iins apart longitudinally of the tubing, so that, in fabricating the unit, the ns are self-spacing and the necessity of positioning the fins in spaced relation by apparatus during the insertion into and the expansion of the tubing in the holes in the fins or the labor in so positioning them, will be eliminated.

Another object of the invention is to provide a heat exchange unit in which the tubing is expanded into interlocking relation with the crossfins, and in which the cross-fins are provided along their outer margins with twisted tongues or teeth between alternate flat portions of fins for deflection of the air passing between the iins, to produce more efficient heat transfer.

Another object of the invention is to provide an improved method for fabricating cross-finl heat exchange units which includes cross-fins interlocked with expanded portions of a coil of tubing, which comprises providing integral tongues or teeth along the margins of alternate fins for spacing the fins, so that the entire group of iins can be pressed'together during the insertion into and the flattening of the tubing for interlocking engagement with the iins.

Other objects will appear from the detailed description.

The invention consists in the several novel features which are hereinafter set forth and more particularly defined by claims at the conclusion hereof.

In the drawings- Fig. l is an elevation of a heat exchange unit embodying the invention, viewed from the side at which the fins are provided with slots for the entry of the tubing in the holes in which the tubing is expanded;

Fig. 2 is a perspective of one of the at ns;

Fig. 3 is a perspective of one of the ns provided with twisted teeth along its margins;

Fig. 4 is a section through a portion of the tubing and illustrating the flattened tubing interlocked with a flat iin;

Fig. 5 is a side elevation of a portion of the unit viewed from the opposite side of Fig. 1; and

Fig. 6 is a section taken on line 6 6 of Fig. 5.

The heat exchange unit comprises a continuously formed serpentine coil of tubing, which includes parallel reaches I0 serially connected by integral return bends II and cross-fins xedly held on and spaced along the straight reaches of the tubing. All of the fins are formed with apertures I8 and slots 20 intersecting one edge of the fins and the rims of the apertures for the side entry of the parallel reaches of thetubing into said apertures while the tubing has its normal or initial diameter. The apertures I8 are of greater width or diameter than the slots 20, and the slots correspond in Ywidth substantially to the diameter of the tubing before it is secured in the fins. After the sidewise insertion of the tubing into the apertures I8, the tubing is attened as at YI lin and thereby expanded transversely into tight interlocking relation with the edges of the apertures 20, as illustrated in Fig. 4, to secure the iinsand tubing in heat-conducting relation.

The fins include a series of fiat tins I4 and'a series of fins I6 provided with integral oiset spacer tongues, the fins of one series being alternately disposed between the fins of the other series. Fins I6 are provided along their contnuous edge with a series of twisted tongues 22, the outer ends of which extend diagonally between the ilat I-lns I4. Along the opposite edges of ns I8, which are interrupted by slots 20, these fins are provided with oppositely twisted tongues 24 which extend between flat portions 26 at the sides of slots 20. These twisted tongues along the opposite side-edges of the iins function to symmetrically space the fiat fins transversely apart along the tubing and to space the fins I 6 symmetrically between the fins I4. The outer corners of the twisted tongues engage the contiguous fiat iins and space the fiat central portions of fins I6 between the fiat fins I 4.

Besides functioning as spacers, the twisted or helical tongues cause the air entering and leaving the portion of the spaces between the central portions of fiat fins I4 and the iiat central portions of fins I6 to be deiiected for more efficient heat transfer by the contact of the air with the fins, and because the tongues extend angularly across the spaces between the fins.

In fabricating the unit, the tubing is bent to form the coil with integral straight reaches I0 and return bends II with the tubing normally of a diameter, which permits it to pass through the slots 20 and into the apertures I8 in the iins. The fins I4 are cut from a strip of metal and punched to form the apertures I8 and slots 20, according to the spacing of the parallel reaches of the coil. The fins I6 are cut from a strip of contiguous faces of the fins. The resiliency of I the tongues cause their outer corner to insure contact between the iiat ns I4 and the tongues when the fins are pressed together. The reaches I0 of the coil are then passed sidewise through the slots 2U into the apertures I8. The portions of the straight reaches of the coil, which extend through the series of tins, are then simultaneously flattened as at II'Ia by a suitable die to expand the tubing in the apertures I8 and transversely interlockthe iins and coils. The tongues result in self-spacing of the ilus during the fabrication of the unit, so that it is not necessary to provide a jig or frame for relatively positioning the fins during the fabrication of the unit. This effects a great saving in the cost of fabrication.

In the completed coil thus fabricated, the corners of the tongues, as the result of the end pressure applied to the entire group of tins during fabrication, resiliently contact the contiguous ns and deflect the air between the fins, which results in high thermal transfer efliciency.

The invention exemplifies a heat transfer unit of the type which includes cross-fins with sideentry slots for a continuously formed coil which can be fabricated at a low cost and possesses high eiiiciency.

The invention is not to be understood as restricted to the details s'et forth, since these may be modified within the scope of the appended claims without departing from the spirit and scope of the invention.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is:

1. A heat transfer unit comprising: a. coil of tubing including straight reaches and integral return bends, and cross-fins provided with slots for the side-entry of the coil into apertures in which the tubing is expanded for transversely interlocking the fins and coils, and with series of slits extending inwardly from their edges and resilient helically twisted tongues extending between the slits for spacing the fins along the tubing.

2. A heat transfer unit comprising: a coil of tubing including longitudinally extending reaches and aY return bend, and series of alternately arranged cross-ns provided with slots for the sideentry of the coil and apertures in which the tubing is expanded for transversely interlocking the fins and coils, one series of ns having substantially flat edge portions and the other series having integral offset tongues along their edges and extending between said at edge portions, for spacing the iins apart along the tubing.

3. A heat transfer unit, comprising: a coil of tubing including longitudinally extending reaches and a return bend, and series of alternately arranged cross-fins provided with slots for the sideentry of the coil and apertures into which the tubing is expanded for transversely interlocking the fins and coils, one series of iins being substantially flat and the other series having integral resilient twisted tongues along their edges projecting transversely from both faces of the fins of such other series and extending between said flat fins, for spacing the fins apart along the tubing.

RICHARD W. KRITZER.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,826,344 Dalgliesh Oct. 6, 1931 2,023,739 Mason Dec. l0, 1935 2,092,170 Kritzer Sept. 7, 1937 FOREIGN PATENTS Number Country Date 126,083 Australia 1931 

